蛋壳比金属还要坚硬小鸡如何破壳而出英语美文

　　It’s been a tough one to crack, but scientists say they have zoomed in, to an unprecedented degree, on the structure of shells surrounding chicken embryos, revealing how they change to allow young birds to hatch.

　　科学家说他们以前所未有的程度对蛋壳的结构进行放大并进一步了解，揭示了它们如何改变以允许幼鸡孵化。

　　Before being laid, bird eggs form a hard calcium-rich shell with three main layers. While it was already known that these thin from the innermost out as a chick grows in preparation for hatching – with calcium from the shell being incorporated into its skeleton in the process – quite what happens at the molecular scale has been something of a mystery.

　　鸡蛋离开母体时蛋壳富含钙质，蛋壳有3层构造，小鸡在蛋壳中一点点成长起来，在这个过程中，蛋壳由内到外变薄，来自蛋壳的钙质也会被小鸡的骨骼吸收。但在分子尺度上这一过程至今还是秘密，到底是怎么发生的呢?

　　Now scientists say they have discovered that eggshells have a nanostructure, and that it appears to play a key role in the strength of the shell.

　　现在科学家们说他们已经发现蛋壳具有纳米结构，并且它似乎在贝壳强度方面起着关键作用。

　　“Everybody thinks eggshells are fragile – [when] we’re careful, we ‘walk on eggshells’ – but in fact, for their thinness they are extremely strong, harder than some metals,” said Prof Marc McKee, a coauthor of the study from McGill University in Canada. “We are really understanding now at the almost molecular scale how an eggshell is assembled and how it dissolves.”

　　“每个人都认为蛋壳很脆弱，当我们小心翼翼，我们走在蛋壳上时，但事实上，由于它们的纤薄，它们比一些金属更坚硬，更硬，”该研究的合着者来自加拿大麦吉尔大学马克麦基教授说。 “我们正在了解蛋壳的组装方式和分解过程。”

　　Writing in the journal Science Advances, McKee and colleagues describe how they probed the issue by focusing on the role of a protein known as osteopontin. This substance is found throughout the eggshell and was already thought to be important in organising the structure of its minerals.

　　McKee及其同事在“科学进展”杂志上撰文，并描述他们如何通过关注骨桥蛋白这一蛋白质的作用来探讨这个问题。这种物质在整个蛋壳中均可发现，并已被认为是组织其矿物结构的重要组成部分。

　　“Something as different as an eggshell and a tooth and a bone, they all have this protein,” said McKee. “We think it is proteins like that that help guide the mineralisation process to give these tissues their properties.”

　　“像蛋壳，牙齿和骨头那样不同的东西，它们都含有这种蛋白质，”麦基说。“我们认为这些蛋白质能够辅助矿化过程，并赋予这些组织特性。”

　　Using a number of microscopy techniques, as well as a cutting-edge method known as focused-ion beam for preparing thin sections of the eggshell, the team found that all of the layers appear to be formed from an array of tiny areas packed with a crystalline calcium-containing mineral.

　　通过采用许多显微镜技术，以及称为聚焦离子束的尖端方法来制备蛋壳薄片，该团队发现所有层都是由一系列小区域的结晶含钙矿物构成。

　　The team also found the areas are smaller and more closely arranged in the outer layer, with the nanostructure becoming larger towards the inner layers. Levels of osteopontin were found to be lowest in the innermost eggshell layer.

　　研究小组还发现，外层的面积更小，排列更紧密，纳米结构朝内层方向变大。同时发现骨桥蛋白含量水平在最内层的蛋壳层中最低。

　　“The third discovery was that the outside of the shell is harder as it has the smallest [nanostructure] and then you move inwards and it gets a little bit softer,” said McKee.

　　“第三个发现是，外壳的外部更硬，因为它具有最小的纳米结构，然后你向内移动，它就会变得更柔软一点，”麦基说。

　　The team say the upshot is that osteopontin seems to form a sort of scaffold that guides the arrangement of calcium-containing mineral, generating a nanostructure that affects the hardness of the eggshell layer.

　　该团队说，骨桥蛋白似乎形成一种指导含钙矿物排列的支架，从而产生影响蛋壳层硬度的纳米结构。

　　McKee says the theory is backed up by experiments in the lab.

　　麦基说这个理论是由实验室试验支持的。

　　“If you don’t put in the protein in the test tube you get a big giant calcite [calcium carbonate] crystal like you’d find in a museum. If you throw in the protein, it slows the process down, it gets embedded inside that crystal and it generates a very similar nanostructure property in those synthetic crystals and they have increased hardness,” said McKee. Higher concentrations of osteopontin were found to produce a smaller nanostructure.

　　“如果你不把蛋白质放进试管里，你会得到一个巨大的方解石(碳酸钙)晶体，就像你在博物馆里找到的那样。如果你投入蛋白质，它减缓了整个过程，它嵌入到晶体内部，它在这些合成晶体中产生非常类似的纳米结构性质，并且提高硬度，“McKee说。较高浓度的骨桥蛋白能够产生较小的纳米结构。

　　The team then turned from the eggs that wind up on our breakfast tables to looking at the structure of chicken eggs that had been fertilised and incubated for 15 days. While the nanostructure of the outermost of the three eggshell layers remained unchanged, the nanostructure of the inner layers had become smaller in size. That, said McKee, is a result of calcium carbonate being dissolved in acidic conditions and used in the chick’s skeleton, and the process might be aided by the nanostructure increasing the surface area of the calcium-containing mineral.

　　然后团队从早餐桌上的鸡蛋转向查看已经受精并孵育15天的.鸡蛋的结构。虽然三个蛋壳层最外层的纳米结构保持不变，但内层的纳米结构尺寸变的更小。McKee说，这是碳酸钙在酸性条件下溶解并用于小鸡骨骼成长的结果，并且该过程可能为纳米结构提高含钙矿物表面积提供帮助。

　　The upshot is that the shell weakens, allowing it to crack and the chick to hatch.

　　这样的结果是壳被削弱了，使得小鸡孵化，蛋壳破裂成为可能。

　　While the role of other proteins in the structure of eggshell layers has yet to be unpicked, McKee said the latest findings could prove useful in the design of new human-made materials.

　　虽然其他蛋白质在蛋壳层结构中的作用尚未被揭露，但McKee说最新的发现可能在新型人造材料的设计中具有指导作用。

　　“When you think about it, we should be making materials that are inspired by nature and by biology because, boy, it is really hard to beat hundreds of millions of years of evolution in perfecting something,” he said.

　　“当你思考这个问题时，我们应该寻求来自于大自然和生物学的材料，从中获取设计材料的灵感，因为这些经历了数亿年的进化是东西可以说是近乎完美的”他说。

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